Pranayama incorporates right nostril breathing (RNB or surya anuloma viloma), left nostril breathing (LNB or chandra anuloma viloma) as well as alternate nostril breathing (ANB or nadishudhi). It is of interest to note that when all the three techniques were practiced for the same frequency and duration, interesting results were obtained (Satendra Singh, 2009). Keeping this in view, the present study is designed to determine whether Nadi-shodana pranayama practice for 30 minutes duration has any influence on the selected cardiorespiratory parameters and cardiorespiratory fitness among the high school boys. To achieve the purpose of this study 30 high school boy's age ranged from 13 to 16 years were selected from a Higher Secondary School - Chennai. They were divided into two equal groups namely the experimental and control groups. They did not have any previous training in Pranayama. They were highly motivated to involve in the training. The experimental group was treated with Nadishodhana pranayama training for five days a week with thirty minutes duration in the evening session for a period of six weeks. The control group was left to follow regular routine. All the selected cardiorespiratory parameters and cardiorespiratory fitness were measured before and after six weeks of Nadi-shodhana Pranayama' training. The analysis of covariance revealed that the experimental group namely the nadishodhana pranayama training group has shown significant improvement on cardio respiratory parameters and cardio respiratory fitness variables namely resting heart rate, systolic blood pressure, diastolic blood pressure, breath holding time, VO, max and cardio-respiratory endurance, when compared to the control group. From this study, it is concluded that Nadi-shodhana Pranayama practice can be advocated to improve cardiorespiratory parameters and cardiorespiratory fitness among high school boys. Further, the positive results found in the present study can be applied to all school students to improve the pulmonary functions of the students. A few minutes practice daily may help in setting the mind better on work and studies. The daily practice could maintain better physical and mental health to have a better future.